The manufacturing of jewels is so ancient it is impossible to date. The Louvre collections show that certain classic setting techniques of precious stones on bezels, still utilized nowadays, were already known in antique Egypt. The slipping of bezels on wire-like supports (e.g. golden chains) has also been known for a long time, such as for the manufacturing of necklace and bracelets. The basic technique is simple, for it suffices to drill a hole within the bezel, through which the wire-like support is inserted.
More complex are the techniques aiming at immobilizing the bezels on the wire-like support in order to prevent slipping of the bezel or even rotation of the bezel around the axis of the support, whenever it is compulsory to always present the same decorative face.
An ordinary technique allowing for immobilization in translation of the bezel consists in mounting stop rings on each side of the bezel and in setting the stop rings on the wire-like support. This technique is however tiresome, costly because of additional material, and the result is often unaesthetic.
Another technique consists in injecting glue between the bezel and the wire-like support, thereby providing double immobilization: both in translation and in rotation. However, it requires additional material, the mechanical properties (especially resistance to fatigue) and physic-chemical properties (especially resistance to oxidation) may appear uncertain and not constant in time. Moreover, the final result may appear unaesthetic, especially when the injection technique is not well mastered, or whenever the glue viscosity and drying time are not adapted (e.g. glue is too fluid or on the contrary too viscous; the drying too slow, or on the contrary too fast).
Those drawbacks are much important in the manufacturing of jewels of complex structure or, moreover, of small dimensions, since at the millimetric scale (and below), the effects of friction (capillarity) are greater than the effects of gravity, and the precise applications of glues is extremely tricky. This is why turning to mechanical techniques of immobilization is required.
It is known from European patent application No. EP 1 819 523 a technique consisting of creating a roll on the wire-like support inside the bezel for immobilizing the bezel in translation and, whenever possible, in rotation.
Practically, this technique is presently utilized on a large scale for the manufacturing of jewels including a wire made of a thermoplastic transparent material (such as fishing line), on which bezels are slipped, embedding precious stones such as diamonds. After having inserted the wire in the bezel, one introduces in the bezel the tip of a welding iron, which is applied at the end of the wire. Under the heat, a spheroid roll forms at the end of the wire, within the bezel. This operation may be symmetrically repeated, such that both rolls thus created, having a diameter greater than the holes in the bezel, thereby immobilize the bezel on the wire at the desired position. This technique, together with the interesting mechanical properties of the fishing line (altogether flexible, resistant to traction, to torsion and to shearing), makes it possible to realize jewelry of complex forms (such as a butterfly).
The general satisfaction of clients made the commercial success of those jewels possible. The attention of the inventors has however been drawn to some cases of dissociation of the wire and bezel, allowing at least the rotation of the bezel, and even—although less often—their separation.
Studies conducted by the applicant have permitted to identify three main causes to those incidents:                some clients' habit to constantly handle their jewel, rotating the bezel between the thumb and index, the cyclical solicitations thereby loosening the bezel on the wire;        the wire loosing resistance when exposed to light, since nylon is known as sensitive to ultraviolets;        the rupture of the wire and the forming of rolls potentially being less precise and repetitive during the application of the welding iron.        